Trilete Spores
1. With perine; perine tight fitting and densely verrucate
Pteridium aquilinum
1’ Without perine
2. Psilate-scabrate or with negative sculptural elements
3. Psilate-scabrate
4. Laesurae with lips; exine >1.5 micrometers thick
Adiantum or Dennstaedtia (includes Adiantum pedatum)
4’ Laesurae simple, short; exine <1.5 micrometers thick; (spore sub-angular and somewhat compact latitudinally)
Pteridium aquilinum
3’ Spore concave in polar view; Foveolate (a negative reticulum with wide muri)
Lycopodium lucidulum
2’ Not scabrate; scupltural elements positive; structure may be restricted to distal surface (especially Sphagnum)
5. Sculpture radially extended: bacculate or verrucate
6. Sculpture bacculate (not echinate); bacculae twice as long as broad and not fused
Osmunda cinnamonea
6’ Sculpture verrucate (can vary from undulating to verrucate in Sphagnum)
7. Laesurae without lips; 30-35 micrometers
Botrychium virginianum
7’ Laesurae with lips; <30 micrometers, if >30 micrometers could be Botrychium simplex-type
Sphagnum
5’ Sculpture reticulate
8. Reticulum extending well on to proximal surface
9. Nodes at angles of muri
Lycopodium clavatum
9’ Without nodes
Lycopodium complanatum
8’ Reticulum not extending onto proximal surface
10. Laesurae about two-thirds spore radius, lumina small (up to 7 micrometers)
Lycopodium obscurum
10’ Laesurae reaching equator; lumina larger
Lycopodium annotinum
